Javascript RegExp match & Multiple backreferences

Question

I'm having trouble trying to use multiple back references in a javascript match so far I've got: -

function newIlluminate() {
  var string = "the time is a quarter to two";
  var param = "time";

   var re = new RegExp("(" + param + ")", "i");

    var test = new RegExp("(time)(quarter)(the)", "i");

  var matches = string.match(test);

  $("#debug").text(matches[1]);

}

newIlluminate();

#Debug when matching the Regex 're' prints 'time' which is the value of param.

I've seen match examples where multiple back references are used by wrapping the match in parenthesis however my match for (time)(quarter)... is returning null.

Where am I going wrong? Any help would be greatly appreciated!

Your regex test simply doesn't match the string (as it does not contain the substring timequarterthe). Do you want alternation? — Bergi
– Bergi, Commented Aug 17, 2013 at 13:24
Ideally I want to loop through the matches in the string and wrap each in a span. So I would expect matches[1] = time, matches[2] = quarter etc. — KryptoniteDove
– KryptoniteDove, Commented Aug 17, 2013 at 13:27

Niet the Dark Absol · Accepted Answer · 2013-08-17 13:26:29Z

1

Your regex is literally looking for timequarterthe and splitting the match (if it finds one) into the three backreferences.

I think you mean this:

var test = /time|quarter|the/ig;

answered Aug 17, 2013 at 13:26

Niet the Dark Absol

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2 Comments

Niet the Dark Absol Over a year ago

That's because it's the first match. g changes the behaviour so that it returns all matches in the order they are found.

KryptoniteDove Over a year ago

Yeah i figured that out seconds after my comment, had my head in this too long going nowhere thanks both! marked as answer because it was first :)

Bergi · Accepted Answer · 2013-08-17 13:27:25Z

1

Your regex test simply doesn't match the string (as it does not contain the substring timequarterthe). I guess you want alternation:

var test = /time|quarter|the/ig; // does not even need a capturing group
var matches = string.match(test);

$("#debug").text(matches!=null ? matches.join(", ") : "did not match");

answered Aug 17, 2013 at 13:27

Bergi

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